Astronomers have discovered more than 16,000 near-Earth objects — asteroids and comets whose orbits bring them into our cosmic neighborhood. But experts believe the actual number is far higher — perhaps in the millions.
Asteroids measuring 0.6 miles (965 meters) wide or larger could threaten civilization if they were to make impact. Scientists believe they’ve identified about 95 percent of objects that large, and none of them poses a threat to Earth for the foreseeable future.
NASA estimates that about once every 10,000 years, a space rock 100 meters or larger strikes Earth, devastating the surrounding area and producing dangerous tidal waves.
The asteroid 2014 JO25 made its closest approach to Earth on April 19, 2017, coming within 1.1 million miles of the planet — about 4.6 times the distance between the Earth and the moon. This map shows the asteroid’s locations as it passed through the sky April 19 to April 22.
Animation showing the motion of a bus-sized asteroid, known as 2016 RB1, on Sept. 6, 2016.
Scientists discovered the object just two days before it passed within 23,900 miles of Earth — about one-tenth of the distance between Earth and the moon.
Credit: Gianluca Masi, The Virtual Telescope Project
Christmas Eve asteroid
These images of an asteroid 3,600 feet (1,100 meters) long were taken on Dec. 17, 2015 (left) and Dec. 22, 2015 by scientists using NASA’s giant Deep Space Network antenna at Goldstone, California.
This asteroid safely flew past Earth on that Christmas Eve at a distance of 6.8 million miles.
This graphic depicts the orbit of asteroid 2014 RC around the sun.
The house-sized asteroid will flew past Earth on Sept. 7, 2014, at a distance equivalent to about one-tenth of the span between Earth and the moon.
This graphic depicts the passage of asteroid 2004 BL86, which came within about three times the distance from Earth to the moon on Jan. 26, 2015.
Asteroid 2016 QA2
Orbit diagram for the newfound asteroid 2016 QA2, which flew by Earth on Aug. 28, 2016.
They call it a Trojan asteroid because it basically its orbit with a planet and has an almost identical orbital period. Thousands of Trojan asteroids are known to share Jupiter’s orbit, while others have been found sharing orbits with Neptune and with Mars. This one, called Asteroid 2010 TK7, was identified in July 2011. The first Earth trojan asteroid to be discovered, 2010 TK7, which measures about 1,000 feet in diameter, precedes Earth in its orbit around the Sun.
Relatively close call
This was a relatively close call. An asteroid known as 2011 CQ1 got discovered February 4, 2011, and then made a record close Earth approach 14 hours later, getting as close as 3,405 miles (5,480 kilometers).
Close but no threat
In October 2010, a relatively small asteroid known as 2010 TD54 flew past Earth, getting as close as 27,960 miles. The odds of an impact were put at zero. Not that it would have been a big deal if the calculations were off: 2010 TD54 was estimated to be about 16 to 33 feet wide. If an asteroid of the size of 2010 TD54 were to enter Earth’s atmosphere, scientists say it likely would burn up high in the atmosphere and cause no damage to Earth’s surface.
Closer than the moon
A 400-meter-sized asteroid known as 2005 YU55 was expected pass within 0.85 lunar distances from the Earth on November 8, 2011.
Small but close
In June, near-Earth asteroid 2011 MD came within 7,500 miles of the Earth’s surface. Again, it was a relatively small asteroid, measuring between 5 and 20 meters in diameter. Astronomers say that objects of this size come this close to Earth about every 6 years on average.
Comet Elenin started breaking up in August 2011 after being blasted by a huge solar storm, and a close pass by the sun on Sept. 10 apparently finished it off. The leftovers of Elenin won’t return for 12,000 years